South Beijing area is covered with Cenozoic sediments, so underground geological structures are unclear. Through a synthetic analysis of numerous geophysical data and consulting available geological and borehole data, the authors inferred various fractures, computed the depth of the pre-Cenozoic bedrock surface, defined the main geophysical-geological boundaries and lithological formations, discussed the division of tectonic elements, got a clear understanding of geological structures and put forward some new opinions. The results obtained will grow an important role in geological structural studies of Beijing area and are hence of great significance in Beijing's economic development.